There are a wide variety of applications where heated or chilled fluid is delivered over a length of conduit such as a hose or pipe. Typical industrial applications include fluid coatings or adhesives that are applied at specific assembly or processing stations in a plant. The fluid may thus be stored in an area remote from the one or more dispensing stations. Many commonly used industrial compositions vary in viscosity with changes in temperature. For example, spray coating thickness, texture and cure time may all be affected by variations in the viscosity of the sprayed materials. Improved reliability and repeatability of dispense patterns and characteristics in industrial processes are a benefit of maintaining the temperature of the applied materials within a pre-selected range. It is generally preferred to perform the bulk temperature control at the point of introducing the fluid into the system, particularly where there are multiple application points. During delivery of the fluid to the application station, a change in fluid temperature can result if the ambient temperature varies from the initial control temperature. The temperature gradient increases as the difference between the ambient temperature and control temperature increases and as the length of the conduit increases.
Engineers have developed various means for achieving the desired temperature control. Once such design is a flexible cover assembly having thermal fluid transfer tubes attached or embedded therein. Such an assembly is known from U.S. Pat. No. 5,363,907 to Dunning et al. In Dunning, the cover is secured about a fluid supply conduit, and heated or chilled fluid is passed through the tubes. This design has met with significant success, however, the materials heretofore utilized in the assembly tend to be relatively insulative. These materials, typically in the form of elastomeric, cylindrical tubes are generally ineffective in transferring sufficient heat between the fluid supply conduit and the thermal transfer fluid to aggressively change the temperature of the fluid in the conduit.
An alternative design relates to coaxial hoses or pipes wherein a thermal transfer fluid is passed through the space between the outer diameter of an inner hose or pipe and the inner diameter of an outer hose or pipe. One such design is known from U.S. Pat. No. 5,287,913 to Dunning et al., herein incorporated by reference. Such a design has been demonstrated to be more effective in aggressively changing the temperature of fluid in the fluid supply conduit than tube-in-cover designs, however, the outer hose may have a tendency to buckle or kink, and therefore block fluid flow when the coaxial assembly is bent or flexed. Thus, the hose can collapse in certain high motion applications, potentially resulting in mixing of fluids from the inner and outer hoses, or breaking and spillage of thermal transfer fluid out of the outer hose. A related concern involves the necessity for securing the hose with clamps at various points. Where the coaxial hose is used to deliver fluid to a movable spray device, for example, it may be necessary to clamp the hose to portions of the movable device at various points. In order to avoid collapsing of the hose from clamping force, designers have typically used a relatively bulky, heavy duty, spiral wound reinforced hose.